The present invention is generally related to devices, systems, and methods for manipulating materials within and/or separating materials from fluids. In exemplary embodiments, the invention provides an acoustic or ultrasound filter for removal of microbubbles or other target matter from a fluid, particularly for target matter having acoustic impedances and/or densities which are significantly different than that of the remaining fluid. Separation of microbubbles and other matter from biological fluids can be (for example) beneficial for removing microbubbles from blood before introduction of the filtered blood into the patient during cardiopulmonary bypass systems, when using cell-saver systems that filter and return blood that might otherwise be lost during surgery, for dialysis treatment, and the like.
A number of different types of treatments rely on external processing of the blood of a patient. An example of external blood processing is often included in heart surgeries that involve cardioplegia, in which beating of the heart is temporarily halted. During cardioplegia, pumping of the blood through the vascular system, and re-oxygenating the blood can be performed outside the patient's body by a heart-lung machine of a cardiopulmonary bypass system. While the patient is relying on the cardiopulmonary bypass system, the blood flows in a continuous stream from the patient, through the heart-lung machine, and back into the patient. Similarly, patients with compromised kidney function rely on dialysis treatments in which the blood flows from the patient, through the dialysis machine, and back into the patient.
In general, biological fluids that are to be introduced into a patient are handled and processed with great care. This can be relatively challenging during dialysis treatments, cardiopulmonary bypass, and other procedures in which a stream of fluids are removed from the body, processed outside the body, and reintroduced into the body. Such treatments often involve filtration, gas exchange, and the like, with the biological fluid passing through pumps, tubing, filter media, and other artificial structures. Bubbles of various sizes can be introduced into the biological fluids by this processing. While removal of larger bubbles can be relatively straightforward, it can be quite challenging to effectively remove microbubbles from blood and other biological fluids prior to introduction into a patient. Small particulates (and other undesirable materials that are difficult to remove) may also be inadvertently introduced into blood during processing.
While a variety of techniques have been proposed and/or implemented for removal of microbubbles and other impurities from blood and other biological fluids, many known filtration techniques have generally been found to be less than ideal. Hence, it would generally be desirable to provide improved devices, systems, and methods for manipulation and/or separation of target materials from within fluids, particularly from biological fluids. It would be particularly desirable if these improved techniques were compatible with existing biological fluid processing or even facilitated improved biological fluid processing to enhance the safety and efficacy of dialysis treatments, heart-lung machines, and the like. Ideally, such improved techniques would not significantly increase the complexity or cost of the existing blood (and other biological fluid) processing systems, nor increase the difficulty in sterilizing biological fluid processing systems.